Thread-cutting mechanisms for sewing machines



Aug. 1, 1933. A. WOOD THREAD cuw'rnm men/mums F'OR SEWING MACHINES Original Filed Dec. 4, 1931 2 Sheets-Sheet 1 m R w m Aug. 1, 1933. R, D 1,920,944

THREAD CUTTING MECHANISMS FOR SEWING MACHINES Original Filed Dec. 4, 1931 2 Sheets-Sheet 2 Patented Aug. 1, 1933- UNITEDTSTATES THREAD-CUTTING MECHANISMS FOR SEWING MACHINES Alfred R. Wood, Bridgeport, Conn., assignorto The Singer Manufacturing Company, Elizabeth, N. 5., a Corporation of New Jersey Original application December 4, 1931, Serial No.

578,966. Divided and this; application December 1, 1932. Serial No. 645,186

2 Claims. (Cl. 112-252) This invention relates to sewing machines of the buttonhole sewing type and more particularly to machines of this type which are adapted for the sewing of round eyelets.

The invention has for an object to provide a buttonhole machine with improved needlethread cutting and nipping mechanism which is so arranged and mountedon the work-clamp as not to obscure vision of the area of the work exposed Within the upper clamp-feet of the work-clamp for the action of the sewing instrumentalities. A further object of the invention is to combine the'movable thread-cutter and -nip- I per blade with the clamping feet of a workclamp separated by a median line in such a manner as to eliminate the necessity of extending the stationary cooperating parts of the cutting and nipping device carried by one of the feet across the median line of the work-clamp.

With the above and other objects in View, as will hereinafter appear, the invention comprises the devices, combinations, and arrangements of parts set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which theseveral features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

Fig. 1 is a right side elevation of the bed and standard and associated mechanism of a buttonhole sewing machine embodying the invention. Fig. 2 is a top plan view of the workclamping feet and upper thread-trimmer, and Fig. 3 is a horizontalsection through the machine bed, showing the feed-wheel and certain thread-trimmer-actuating parts in plan.

This application has been divided out of applicants copending application, Serial No. 578,966,

filed Dec. 4, 1931. Except as hereinafter described, the machine is constructed substantially in accordance with the disclosure of the Allen Patents No. 1,162,207, of November 30, 1915, and No. 1,346,102, of July 13, 1920. The frame of the machine includes the bed 1 from which rises the standard 2 01 the usual bracket-arm structure supporting the reciprocating needle 3which, together with the usual under-thread mechanism mounted on the turret 4, constitutes the stitch-forming mechanism which is driven from the main sewing shaft 5. The period of operation of the stitch-forming mechanism is controlled by the usual startand stop-motion device, including the tilting startand stop-control lever 6 which in its vertical position, Fig. 1, arrests the motion of the main sewing shaft 5and in its inclined or tilted position, trips the usual clutch-device 7, associated with'the continuously running belt-pulley 8, and effects the coupling of the main-shaft 5 to such pulley.

There is incorporated in the machine the usual buttonhole-cutter shaft 9 which makes one revolution prior to sewing and then comes to rest, and a second auxiliary shaft 10 which is stationary duringthe operation of the shaft 9 and 5 sewing shaft 5 and makes one revolution after the sewing is completed, to perform certain desired operations after stitching, such as (1) the opening of the work-clamp, (2) the release of the tension device, and (3) the rapid drive of the feed-wheel to restore it to initial position. These shafts 9 and 10 are driven from a continuously running belt-pulley .11, Fig. 3, through suitably controlledone-revolution clutch-devices 12, 13, as fully explained in said Allen Patent No. 1,346,102.

It will sufiice here to explain that the second auxiliary shaft 10 is formed with a crank 14 which is connected by a pitman 15 to an arm 16 fulcrumed coaxially with the feed-wheel 17 and pivotally carrying a spring-pressed pawl 18 which acts upon the tooth 19 on the feed-wheel during the motion of the crank 15 from its dotted line position, Fig. 3, to full line position; rapidly turning the feed-wheel at one sweep from its position at the end of a sewing operation to initial position ready to begin a new cycle of operations.

The machine is equipped with the usual travelling work-clamp including the lower clampplates 20 and upper clamp-feet 21, 22; the work- 90 clamp as a whole being moved longitudinally and laterally over the bed 1 to place the stitches about the buttonhole by the usual connections with the longitudinal-feed cam-groove 23 and lateral-feed cam-groove 24 in the feed-wheel 17. '95 In the present instance the cam-grooves 23 and 24 are so shaped as to move the work-clamp in a path to effect the sewing of a round eyelet.

The machine is preferably equipped with needle-thread cutting mechanism constructed substantially as follows: The upper clamp-foot 22 has pivotally mounted thereon at 25 an upperthread trimmer-device 25' constructed substantially in accordance with the disclosure of the Allen Patent No. 885,310, of April 21,1908, but is distinguished from the disclosure of said patent by being arranged and operated so as to perform its closing or cutting-and-nipping movement toward the side of the clamp-foot 22 and away from the median line a-a of the work-clamppllo instead of at the end of the clamp-foot and in the direction of the median line, as heretofore. This arrangement requires a reversal of motion of the pivot-shaft 25 and its actuating crank-arm 26 which is now connected by the link 27 to the reversing lever 28 fulcrumed at 29 on the clampframe and having connected to its upper end the usual push-rod 30 and spring 31; said spring tending to hold the trimmer device 25" in closed position. x

Provision is made for actuating the trimmer device. 25' twice for each buttonhole-producing cycle, once after the initial stitches have been formed to release and retrim the beginning end of needle-thread, and again at the close'of the stitching operation to cut the needle-thread and hold the end thereof leading' from'the needle. In my copending application Serial No. 391,589,

filed September 10, 1929, I have shown and de-- sewing has been well started, engages the arm 33' on the vertical rock shaitii l and rocks the latter in a direction to cause the. bent arm 35 at the upper end of the rock-shaitB to engage and swing forwardly the arm 36 of .thethread-trimmer opening bell-crank lever 36, 37, which engages the push-rod .30 andshoves it to theleft, Figl. Whenthe heel 38 of the-cam 32 passes the arm 33, the push-rod 30 is suddenly released and the spring 31 closes the trimmer and nipper devices 25' which retrims the beginning needlethread end.

When the sewing is completed and the second auxiliary shaft 10 is given its single rotation to restore the feed-wheel 17 to initial position, a cam 39 cm the shaft 10 elevates the link 40 connected to the lever e1 which carries a pin 42 engaging the forked rear end of the bell-crank lever-arm 37 and actuates the trimmer and nipper device 25 a second time.

Having thus set forth the nature of the invention, what I claim-herein is:

1. In a buttonhole' sewing machine, the combination with a work-clamp having right and left clamp-sections divided by a median line and each including an upper clamp-foot, of a thread-trimmer and nipper device pivotally mounted on the clamp-foot of one of said sections in position to perform its closing movement toward the side of said clamp-foot and away from the median line of the work-clamp, and means for opening and closing said device. I

2. In a buttonhole sewing machine, the combinationwith a work-clamp having right and left clamp-sections divided by a median line and each including an upper clamp-foot, of a threadtrimmer and nipper device pivotally mounted on the clamp-foot of one of said sections in position to perform its closing movement toward the side of said clamp-foot and away from the median line of the work-clamp, and means for opening and closing said device, said means including a pair of endwise movable rods and a motion-reversing device mounted on the work-clamp and con meeting said rods together for simultaneous movements in opposite directions.

ALFRED R. WOOD. 

